Effects of freeze–thaw cycles on the properties of polyethylene geomembranes

Abstract

High-density polyethylene (HDPE) geomembranes (GMs) are frequently used as fluid barrier components of cover systems for mine site reclamation in regions that are prone to freeze–thaw cycles (FTCs). However, HDPE GMs are more susceptible to stress cracking than linear low-density polyethylene (LLDPE) GMs. Hence, LLDPE GMs are increasingly considered as alternatives to HDPE GMs in cover systems. Nevertheless, little information is available on LLDPE compared to HDPE GMs. Moreover, little is known about the changes in the fluid barrier properties (the equivalent hydraulic conductivity and the oxygen sorption and diffusion coefficients) for these two materials with FTCs. The purpose of this study is therefore to compare the effects of FTCs on the tensile, hydraulic, and oxygen sorption and diffusion properties of HDPE and LLDPE GMs. To do so, GM sheets were subjected up to 300 FTCs. Mechanically, both GMs got stiffer and their tensile break properties increased with increasing number of FTCs. However, although the GM fluid barrier properties changed with FTCs, the equivalent hydraulic conductivity and the oxygen permeation coefficient remained within an order of magnitude of 10−14 m/s and 10−13 m2/s, respectively. Up to 300 FTCs would therefore have no adverse effects on HDPE and LLDPE GMs.